Ophthalmometer.



W. 6: G. S. GOWLLAND.

OPHTHALMOMETEH. APPLICATION FILED OCT. 31, 1910- Patented Sept. 8, 19%

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W-. & G. S. GOWLLAND. OPHTHALMOMETER.

APPLICATION FILED 0013.31, 1910.

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THF NORRIS PETERS c0., PHOTO-LITHQ, WASHINGTON. D. C.

W. & G. S. GOWLLAND.

OPHTHALMOMETER.

APPLIUATION FILED OUT. 31, 1910.

1,1 10,197, Patented Sept. 8, 1914.

6 SHEETS-SHEET a.

L. gmuzlani a 61W. 5'. amamuz WWW j 6 k1 Cur THE NORRIS PETERS 00.. PHO7D-LITHO., WASHINGIDN. D. G

W. & G. S. GOWLLAND.

OPHTHALMOMETER.

APPLICATION FILED OCT. 31, 1910. 1 1 1 O, 1 97, Patented Sept. 8, 1914.

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w. & 0. s. GOWBLAND. OPHTHALMOMETBR.

APPLICATION FILED OCT. 31, 1910.

UZ/WMWM/ THE NORRIS PETERS CO.. PHOTO-LITHO.. WASHINGION. D. C.

, manner.

WILLIAM GOWLLAND AND'GHARLES S. GOWLLAND, OF CROYDON, ENGLAND.

OPHTHALMOMETER.

Specification of Letters Patent.

Patented Sept. 8, 1914.

Application filed October 31, 1910. Serial No. 590,088.

To all whom it may concern Be it known that we, TILLIAM GOWLLAND and CHARLES Snrrnrus GOWLLAND, subjects of George V, King of Great Britain and Ireland, and residing at Morland Road, iroydon, in the county of Surrey, England, have invented certain new and useful Improvements in Ophthalmometers, of which the following is a specification.

In ophthalmometers for the determination of corneal astigmatism, as heretofore constructed, the amount of movement imparted to the prisms which multiply the images corresponds to the amount of move ment imparted to the registering means through the medium of which the prisms are moved, and in instruments in which the prisms are moved transversely of the optical axis and are of varying strength, the registering means do not register the correct displacement of the images. It is chiefly this defect which the present invention has been designed to overcome. In carrying out this invention, we move the prisms through the medium of a suitably shaped cam surface, preferably a snail-cam. The term camsurface is to be understood as including a straight but sloping surface which is adapted to move the prisms in the required In instruments as heretofore constructed in which the prisms are moved longitudinally of the optical axis, although the displacement of the images generally corresponds to the amount of movement imparted to the prisms, we nevertheless apply the present invention thereto in order to simpliiy the construction of the instrument and eheapen its production so that any inaccu racy that there may be in the prisms can be compensated for by suitably shaping the cam-surface. Again, by suitably shaping the cam-surface we are enabled to employ tie-centered lenses or other means for multiplying the images. Another object of this invention is to arrange the recording devices concentrically with the optical axis of the instrument so that the construction of the latter is improved and rendered more compact than formerly.

A further object is to adaptthe instrument so as to make it a single position one.

According to this invention, in that class of ophthalmometer in which the prisms for multiplying the images are moved transversely of the optical axis, we fix the plate which carries the markings indicating the rad i of curvature and also the curvature in dioptres, (known as the middle dial to and concentric with the telescoe tube, and on either side of the slides in which the said prisms are mounted we arrange the other registering means comprising movable disks (hereinafter termed registering-wheels) similarly concentric, their opposing or inner faces having flanges one of which overlaps the other. One of the registering wheels is graduated and the other carries a pointer which extends over the edge of the graduated registering wheel so as to be capable of use in conjunction with the markings on the middle-dial. On the inner face of each registering wheel we fix a snail-cam. The slides which carry the prisms are provided with means for operatively connecting them with the snail-cams, such means consisting preferably of a roller projecting from each of the said slides. The rollers are kept up to the edge of the cams, so that, when the registering wheels are operated, movement is imparted to the prisms. In ophthalmometers of the class in which the prisms for multiplying the images are moved longitudinally of the optical axis, one of the wheels, constituting the registering means, is provided with a boss having a snail-cam surface formed in one end thereof. The slide which carries the said prisms is in operative connection with the boss, and the cam surface is kept in engagement with a stationary roller provided on the telescope tube, sothat when the bossrotates the necessary movement is imparted to the prisms. In order to provide a F single position instrument, We rotate the prisms, and sometimes the objectives as well, instead of finding the secondary axis by rotation of the mires as formerly.

' In order that this invention may be clearly understood and readily carried into efi'ect,

'we will proceed to describe'the same with reference to the accompanying drawings, of which Figures 1 to 4 show parts of an ophthalmometer in which the prisms are moved transversely of the optical axis.

Fig. 1 shows in elevation an inner view of one of the registering-wheels and the mechanism for moving the prisms, the snailcam shown being one which belongs to the other registering-wheel, the latter having been. removed in order to expose the said niecha 1, to view. Fig. 2 1s a tront elevation ol the mechanism for moving the said prisms, a portionthereof being removed, however, in order to clearly show one of the slides by which one of the usual sets of prisms is moved. F shows the relative position of the two rcgistering-wheels, the mechanism for carrying the said prisms and the inith'lle-dial, the registering-wheels and iniddle-i'ilial being); shown in central section, and the said mechanism in side elevation. Fig. l is a part elevation on a smaller scale) of the left-hand side ot' Fig. 3. 5 to show parts of an ophthalmonieter in which the said prisms are moved longitudinally of the optical axis, Fig. showing. in side elevation the snail cam carried by one of the rec;istering-whecls and encircling the telescope-tube, the cam being shown engaging a roller which connects with the slide for moving the said prisms. Fig. 6 is an end elevation of the right-hand end of Fig. 5, Fig. l is a section on line 'T-7 of Fig. 6. Fig. 8 is a front elevation of a flexible cam, and Figs. 9 and 10 are side elevation and sectional plan respectively, of so much of a keratometer or ophthalmometer as it is necessary to show in order to aid the description of that part of this invention which relates to the provision of a single posi tion instrument. Figs. 11 and 12 are tions across (Z and t respectively oi Fig. 10. Figs. 13 and ltl each show a portion of the flexible cam of Fig. 8 w th a detail oi construction in operative connection therewith; and Fig. 15 shows a modified construc tion of a portion of Fig. 10.

Like letters refer to like parts throughout the drawings.

Referring to l to 4 of the drawings, 1"! represents a portion of the usual telescopetube of the instrument secured to bosses I), which are attached to the guides c, 0. wherein. the slides (Z. (Z, work for the purpose of operating the prisms these being held in place by clips c, c. this arrangement of apparatus, however, being as usual, and forming no part of our present invention. f, f, are the registerinpywheels arranged concentrieally' with the telescope tube a', the wheel f being of disk form and the wheel f, in the :torm of a spider. The outer portion of the wheel f is of openwork construction and has a ring or celluloid fined thereto. as shown in Fig. t. The ring of celluloid f contains the necessary markings. shown at J. as will h 1 e11 understood. and is illuminated by light transmitted through the spider-wheel 7, from the usual lamps (not shown) which illuminate the mires. On the inner face of the registering-wheels f, f. we fix the snail-cams a. g, which may if desired, be fixed in position by means of screws or the like passed through slots formed in them, said slots being for the purpose of adjusting the position of the cams on the registering-wheels j. The cams g, 5 are alike in shape. one of them being shown in face view at g in Fig. 1, and they are arranged so that the telescope tube a passes through them. The slides cl, (Z, are operatively connected. with the snail-cams 9'. 5/, in any suitable manner, but preferably by means of rollers 72., 71., mounted on studs 71, 7b, which project from the slides (Z, (Z, the rollers being; kept up to the edge of the cams by means of helical springs j, which are ill at one end to the guides 0, c, and ..e other end to the slides (Z, (Z. The method of attachment of these springs is shown most clearly in Figs. 1 and 2, j, j, showing where they are attached to the do, and j j showing where they are attached to the slide. .ln Fig. 3 the springs j, are of the same construction and they are arranged in the same way as the springs 7', j. in Figs. 1 and The wheels f, f, with their cams 5/, g, are held friction ti a ht on the bosses Z). Z by means of ordinary spring-collars 7c, fitting into circumferential grooves 0 7) formed in the bosses Z), Z). To the spider-wheel f is fixed a pointer Z which extends over the edge of the wheel j. The portion of this pointer which overlaps the ring; of celluloid f is open, as shown at Z, in order that the markings may be read, an index Z beingprorided on the pointer Z to facilitate this reading. on is the middle-dial which is fixed to the boss Z) by means of a collar m and the radii of curvature marked thereon are read off by means of the inner index Z" of the pointer Z. of is a pointer attached to the telescope-tube a and projecting through a partially circrunterential slot m formed inth-e collar m in order that the amount of rotation of the telescope tube may be read on the middle-dial m. The means for fixing the pointer m in position consist of a tongue or base portion m. forming part of the pointer, tightly fitting" into a shallow recess formed in the inner face of the telescope tube (4, and a keeper m, which fits friction tight inside the telescope tube and retains the tongue or base portion m in pl The flanges on. the inner face of the registering-wheels f, f, are shown at f f*, and it will be seen that they inclose the mechanism which carries the prisms and protect the same from dust.

The construction of the cams g, g, and their action on the prisnrslides (Z, CZ, being alike, it will only be necessary to describe the construction and action of one of them, and this will be done with reference to the one shown in Fig. 1, which is assumed to be llXGCl to its registering-wheel 7. Depending upon the direction of rotation of the registering-wheel f, the cam 9, always bearing as it does on the roller it mounted on the prism slide, will cause the prisms carried bythe slide (Z to be moved in one direction or the other across the optical axis of the instrument. The pitch of the cam is such that for a given angular movement of the regis-z tering-wheel to which 1t is fixed, (no matter at the cam, although truly formed, does not.

produce sufficiently accurate results, due possibly to abnormal irregularities in the prisms, it is rubbed away where necessary in order to produce the required amount of travel of the prisms.

Referring now to Figs. 5 to T, on the telescope-tube a are rotatably mounted the two registering-wheels f, f. g is the cam surface formed in the outer end of the boss fixed to the registering-wheel f. A helical spring j presses at one end on a collar 0 fixed to the telescope-tube and at the other end on the registering-wheel f in orc er to keep the cam-surface always in engagement with a roller 71, which is mounted on a stud it fixed in the telescope-tube a. In the latter two slots at, a, are formed through which screws 9', Q, are passed, screwing into a ring (Z in which the prisms for multiplying the images are intended to be mounted. The heads of the screws 7, project beyond the telescope-tube a and are located in a channel 7' formed in the inner face of the boss As in Figs. 1 to 4-, f is a spiderwheel, which is rotatably mounted on the telescope-tube a, being kept in place thereon between the collar 0 and another collar 9 fixed to the telescope-tube. To this spiderwheel is fixed to a pointer Z extending across to and in front of the taceof the registering wheel 7, which is provided with the necessary markings as in Fig. 4:, the'construction of this pointer being the same as in Fi and a, excepting that the inner inden is dispensed with. Describing the operation of the apparatus shown in Figs. 5 to 7, when the registeringwheel is rotated it is caused to move along the telescope-tube a in one direction or the other, depending upon the direction of rotation, as will be well understood. As the wheel moves along it carries the slide (Z along with it. The pitch of the cam is determined in the same way as the,

pitch of the cams described above in connection with Fig. 1.

In some cases, according to this invention, the cam is one which is flexible, or the path of which is adjustable. in example of such a cam is shown in Fig. 8. In this figure,'s is a frame or skeleton conveniently of channel section at the inner end of which is formed a hole .9 adapted to fit over the telescope tube, slots 8 being provided therein for the purpose of adjustably securing it to the registeringwheels. The flexible portion of this cam is a clock-spring 8 having its inner edge resting on or lying near to the bed of the channel and its outer edge :tree. Screws 8*, 8*, are screwed through the sides of the frame or skeleton and their inner ends bear on the opposite sides of the clock-spring In order to connect this cam with the means which carry the prisms for multiplying the images, said means may be provided with arotatable stud h (Fig.

w iich projects therefrom and is provided with a slit h at its end through which the projecting free edge or the cloclnspring passes, or the stud may be replaced by a pair of rollers 72,, h, (Fig. 1%) arranged so that the free edge of the clock-spring works between them. ll hen the instrument has been set up, the clock-spring s can be adjusted by the screws 3, 8* so as to produce the desired amount oi travel of the prisms for a given movement of the means by which they are operated. I

in some cases, in accordancewvith this in Tention,,we use a cam or the like for the pu pose of giving a regular movementto the said prisms by imparting regular movement to the registeringmeans.

The apparatus shown in Figs. 9, 10, ll, andl2 will now be described. Within the telescope tube a is slidingly fitted an inner body 25 furnished at the end near the eyepiece a of the instrument with a handle 25 which projects through a quadrant slot a formed in the telescope-tube. Within the inner body t is slidingly fitted the prism box (Z and the objective bolt "0. The prism box has a pin d" projecting into a slot 5 formed in the, inner body, and it also carries a sleeve 6 whichis loosely journaled in its exterior surface and carries a pin 2?" project ing through an opening 15 conveniently of rectangularshape formed in the inner body 26, and into a slot (6 in the telescope-tube. The diaphragm, which has two apertures arranged one on each sideot its center in a line at rightangles to the prisms, is arranged between the objectves in the box 11, and has a pin w which projects through a quadrant slot '0 inv the box o, and into a slot 6 in the inner body. I

In operation, he handle 25 is first placed at one end of the slot a and then the axis of astigmatism is found as usual, namely, by rotating the telescope tube a'and the mires by means of the handle This axis ha ing been found, the handle 25" is moved through the entire length of slot (1. thereby causing the prisms to be rotated through an angle of 9O" whereby the secondary axis is obtained without further rotation of the mires as was -formerly the case. It Will thus be seen that the instrument is a single position one. During the rotation of the inner body, the loose sleeve 25 remains stationary, owing to its pin t" engaging the sides oil? the slot at, and the diaphragm is carried around by reason of its pin U) engaging the sides of the slot t, said pin to moving along the slot o in the box e, which latter thus left stationary. Sometimes, however. in accordance with this invention, we make provision for the objectives to be carried around by and with the inner body, which may be done by dispensing with the slot o. The secondary axis having been found, the wheel is rotated in order to more the pri 1. s longitudinally for the purpose of ascertaining the amount of astiginatism. During the rotation of the wheel its cam surface 5/ bears on the pin zi thereby moving it alon the slot a, and consequently the pin (5 travels long the slot the cam SUYCMZB 5 and the p n 27 being kept in en- -u mt with one another by means of the sprin on one end of the prism i le claim:

1. ln ophthahnemeters, the combination with the prism-car Tying means, of abutments there n, cams for operating the prisnr carrying means, and means for heepmg the ahutme and cams in engagement with one inner faces of said registering-wheels and overlapping one another.

in ophthalmometers, the combination with the horizontal tubular portion thereof a registering wheel arranged concentrically therewith, and light-transmitting scale carried by an openwork part of said registeringwheel.

6. ln ophthalinometers, the combination with the horizontal tubular portion thereof, of a pair of registering-wheels arranged concentrically with said tubular portion, a scale on one of said wheels, and a pointer fixed to the other of said wheels and extending to the scale-carrying wheel and overhanging the scale.

7. in ophthaln'iometers, the combination with the horizontal tubular portion thereof, of a ""middle-dial and a pair of registeringwheels all arranged concentrically with said tubular portion, ascale on the middle-dial a scale on one of said wheels, and a pointer fixed to the other of said wheels and extending to and overhanging the scalecarrying wheel and middle-dial 8. In ophthalmometers, the combination with the telescope tube and encircling collar, of a middle-dial arranged concentrically therwith and carried by said collar, said collar having a partially circumferential slot and a pointer attached to the telescope tube and extending through the slot so as to be capable of use in conjunction with the middle-dial In witness whereof we have hereunto set our hands in the presence of two witnesses.

lVILLIAM 'GOl VLLAND. CHAS. S. GUVVLLAND. l v itnesses to the signature of William Gowlland:

CATHERINE Banner, Donn Annie HAWKINS.

ll itnesses to the signature of Charles Septimus Gowlland:

LEONARD C. BLAKE, Gomiis W. WARD.

Gopies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. G. 

